Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$68.54	5.654%	$72.4153	$72.42	$72.40	$72.40
Purchase #2	$219.65	11.683%	$245.3117	$245.31	$245.30	$245.30
Purchase #3	$208.61	4.217%	$217.4071	$217.41	$217.40	$217.40
Purchase #4	$54.99	7.450%	$59.0868	$59.09	$59.10	$59.10
Purchase #5	$111.92	13.831%	$127.3997	$127.40	$127.40	$127.40
Purchase #6	$215.42	10.815%	$238.7177	$238.72	$238.70	$238.70
Purchase #7	$157.78	7.494%	$169.604	$169.60	$169.60	$169.60
7 purchase totals =	$1,036.91		$1,129.9423	$1,129.95	$1,129.90	$1,129.90